Stream drying and stream pollution: similarities in impact on benthic invertebrates

Due to the ongoing climate change which brings unbalanced summer precipitations together with higher evapotranspiration related to rising temperatures, there is an increasing risk of stream intermittency in continental temperate zone. Intermittent streams are exposed to diverse anthropogenic impacts including the input of organic pollution. The discharge of wastewater from sewage treatment plants is one of the most common forms of pollution in stream ecosystems and has adverse effect on benthic invertebrates. The response of stream biota to saprobic pollution is well described in perennial systems. However, the evidence of structural and functional aspects of benthic invertebrate assemblages in polluted intermittent streams is scarce. We analysed the impact of such pollution and flow cessation on freshwater invertebrate community within the dataset of 16 sites from the Czech Republic. Perennial and intermittent sites and polluted and non-polluted sites (4 replicates from each combination) were compared to disentangle the impact of wastewater pollution and flow intermittency. We found that the benthic invertebrate assemblages from four studied groups (perennial non-polluted, perennial polluted, intermittent non-polluted, intermittent polluted) differ. Our results indicate, that this type of water pollution and stream intermittency can have similar yet not the same effect on benthic invertebrates.